The manufacturing industries have developed several types of coatings for glass and other types of transparent and semi-transparent materials. It is also important that the location of any coated surface is known during the manufacturing process. It is especially important that there be a method to distinguish the non-conductive coatings from any type of conductive coatings.
For example, in the coating and glass industry, for example, there are numerous applications where residual coatings from the manufacturing process or spectral reflective coatings are applied to a transparent surface. In particular, for architectural applications, surface coatings are often used on glass to reduce thermal transfer through the glass. The coatings are effective for reflecting and/or absorbing certain wavelengths of solar radiation that strike it. The coatings are generally in the form of an electrically conductive transparent film on one surface of the glass. It is often difficult to visually detect the presence or absence of a solar surface coating on glass.
Further, even when the presence of a solar coating is detected, it is almost impossible to visually detect which side of the glass sheet is coated. It may be desirable to have the coated surface on the interior of the building to protect the coating from the outside environment. The problem may become even more important where a window pane assembly is formed from two spaced sheets of glass. Preferably, a solar coating is placed on the interior surface, i.e., the surface between the two panes, of the outer glass pane. If the coating is located on the inner glass pane, there may be excessive heat buildup between the spaced window panes which could lead to premature failure of the seal between the panes.
Currently, one method for detecting a non-conductive coating uses an optical reflection method where light is emitted onto and reflected from the coated surface. The amount of light energy reflected from a non-conductive coated surface is different from a clear or uncoated surface. However, there is a need to improve this reflection method since there is a vast proliferation of new types of non-conductive coatings. Many of the new non-conductive coating have the same reflection characteristics when exposed to light from a limited spectrum light source (i.e., monochrome light source, Laser, LED, etc.) as the reflection characteristics of conductive LOW E (Low Emissivity) coatings. This inability to easily determine the presence and location (i.e., on which side of glass is which coating) causes a concern since LOW E coating must be on the inside of a sealed window, while many non-conductive coatings are designed for the outside surface of a sealed window assembly. It is thus important that those installing the glass install the glass in the proper orientation.
While there is a currently used method for detecting a conductive coating using a capacitance method, such method does not reliably detect the surface location of the conductive coating and cannot detect the presence or location of non-conductive coatings.
Further, another detection method involves a continuity test device in which a device must touch the coating on the medium. However, this device can damage the coating which is unacceptable.
Therefore, there is a continuing need for an improved, reliable and efficient method and device to detect the presence, location and type of coating applied to various transparent or semi-transparent mediums, or materials deposited directly to the surface or left on the transparent mediums.